Common side effects of Xanax include fatigue, constipation, weight gain, skin rash, difficulty in micturition, ataxia, weight loss, dysarthria, memory impairment, cognitive dysfunction, drowsiness, diarrhea, blurred vision, insomnia, anxiety, increased appetite, decreased libido, and decreased appetite. Other side effects include sexual disorder, hypotension, muscle twitching, and increased libido. See below for a comprehensive list of adverse effects.